The present invention relates to a microscope device for selectively available phase-contrast and relief observation, employing phase and amplitude-varying layers arranged in a pupil plane in the observation ray path, and a diaphragm arranged in the illumination ray path.
Such devices, which are known as "phase contrast" devices are used for making visible certain non-absorbing structures of microscopic objects, such as structures of different index of refraction or of different thickness. Such structures of different optical thickness which are not perceptible by the eye are generally referred to as phase objects.
In order to make such objects visible, so-called "phase rings" are arranged in the observation ray path, generally directly in the exit pupil of the objective employed; corresponding diaphragms are imaged onto these rings, the diaphragms being arranged in conjugate planes of the illumination ray path. Such action on the phase or amplitude of the light associated with different orders of refraction, effectively masks out certain parts of the diffraction pattern established by projection of the source image and as limited by the diaphragms in the illumination ray path.
As the expression "phase ring" indicates, in customary phase-contrast devices such as those described in West German Pat. Nos. 636,168 and 974,173, amplitude and phase-varying shapes in the form of circular rings are applied to or etched on plates and/or optical elements of the objective in the vicinity of its pupil. The optical system of the microscope, consisting of condenser and objective, is used to project corresponding circular-ring diaphragms, usually arranged directly in the rear focal plane of the condenser, precisely onto the phase rings in the objective.
From West German Pat. No. 1,963,604, it is known, in the case of incident illumination, to develop the diaphragm and the phase ring as ring segments so as to be able to arrange both of them in the same plane, in the exit pupil of the objective, which acts at the same time as a condenser. In this situation, the centroid of light transmitted by the ring segments lies on the optical axis of the projecting objective.
West German published (Offenlegungsschrift) applications Nos. 2,523,463 and 2,523,464 describe a so-called "contrast modulation microscope" having a plate arranged in a pupil plane of the observation-ray path and having strip-shaped regions of different transparency. In this microscope, the diffraction pattern is not invaded symmetrically to the optical axis of the objective, and therefore the phase objects which are made visible by this microscope exhibit, in addition, a relief effect similar to that which occurs upon unilaterally oblique illumination of an object.
One disadvantage of the known "contrast modulation microscope" is that the strip-shaped regions of the modulator plate in the observation-ray path must be adapted very precisely in their angular position to the corresponding openings of the condenser diaphragm. This diaphragm or the modulator must therefore be rotatably mounted, for purposes of adjustment. If it is desired to examine the relief picture of a specimen as a function of azimuth, a rotating stage is also required for support of the specimen.
Since the phase rings of the first-mentioned contrasting method and the modulator of the last-mentioned contrasting method are, as a rule, arranged in the pupil of the objective, which, in the case of a very large number of objectives, may lie in the inaccessible interior, and in part even within the lens components, these two contrasting methods are generally not compatible with each other, since a separate series of objectives must be produced for the two systems, each such objective containing the phase ring or modulator, as the case may be, permanently installed therein. The results in a high expense.